Simulations of ionization in a hot cavity surface ion source

Abstract

A new numerical Monte Carlo method based model of a hot cavity surface ionization ion source is presented in this paper. The model, intended to support the studies on ionization phenomena in a widely used class of ion sources, takes into account geometry of the ion source and extraction system, ionizer temperature and other features. The results of ion source efficiency calculations for various configurations of the extraction field are reviewed. The dominant role of the ionizer region near the extraction opening is described. Simulated dependences of ionization efficiency on the working parameters like ionizer length and temperature, ionization potential of the substance, and extraction voltage are discussed. A good agreement of the experimental data (e.g., influence of ionizer temperature, current-voltage curve) and the predictions of the model is found. It is also shown that the contribution to the ionization yield from impact of thermionic electrons accelerated by the extraction field may be significant, especially for the substances of small surface ionization coefficient. The simulation results are compared to the predictions of different theoretical models of the ion source--the obtained simulation data are in accordance both with a well-known Kirchner formula and the so called spherical ionizer model.

Ionisation Efficiency in Conical Hot Cavities

“…This is also pointless in the light of the presented data. The shape of the curves is similar to that obtained in the simulations for the spherical [17] and tubular [13] ionisers. It also resembles the experimental curves obtained for the tubular ioniser case [22].…”

“…In the previous papers a numerical model of hot cavity ion source was presented [12,13]. It is based on the assumption that multiple collisions of atoms with the hot ioniser walls could lead to high ion source ionisation efficiency.…”

Surface Ionization of Radioactive Nuclides - Numerical Simulations

“…The numerical code is an upgraded version of that previously described [12]. The semi-opened cylindrical ionizer of the length L and the radius r has been considered (see Fig.…”

“…Theoretical models of ionization inside hot cavity were extensively studied [69]. Recently, both theoretical [10], and numerical models of ionizations have been developed [11,12] based on the conception that high ionization eciency is an eect of multiple collisions with hot ionizer walls, and also electron impact ionization [13]. The model enabled the studies of ionization eciency as a function of many factors, ionizer geometry (including the spherical one [14]), extraction system properties, ionizer temperature, ionizer/ sample combination etc.…”

Calculations of Ion Beam Emittance for Hot Cavity Ion Source

“…Some attempts were made in order to describe diusion of nuclides in target and eusion in the surface ion sources [1315]. Recently, a numerical model of ionization in hot cavity ion source has been developed [12,16,17], taking into account not only surface ionization but also possible eects of electron impact ionization mechanism [18]. Initially the model was suitable for stable and long-lived isotopes, but radioactive decay and delays due to the diusion and eusion were implemented [12,19], making it useful also for short-lived isotopes, which are common in on-line nuclear spectroscopy.…”